Rocker like noise

[ukrkoz]

Hi all

My son bought 2006 Infinity G35 2 door coupe for his wife.
Apparently, it's oil drinker (40 000 miles). 3 000 miles ago, at start up, engine started making loud knock, as in LOUD. We determined that oil level was low, added oil, engine started fine. We changed oil with good synthetic 5W30.

It's rather cold outside now. She did not drive car over the weekend. Going to work this morning, engine did same loud knock at start up. Son immediately added oil to full on disptick, end it took 3 qrts.

He says that engine now runs OK, but there's crunchy noise at 3 000 RPM and higher. It is V6.

Is this a known issue with those engines? Say, my other son has Mazdaspeed, and had persistent cold start rattle, that was caused by VVT actuator and poor quality timing chain. They even issued recall on this. Mazda, I mean.
So, any ideas what we are dealing with here? Besides obvious - oil drinker.

Help is much appreciated.

Thank you

[RED_DET]

The VQ is known to have oil consumption issues. 3qts low in how many miles (since the last time you did the oil change)? I'm sure there is some damage if there is still noises coming from the engine.

[ukrkoz]

3 000 miles. Since oil change. On my book, it's oil guzzler. I can live with half a qrt per 1 000 miles, but not a qrt.
The way he describes that noise, and he's bringing car here some time next, it sounds like timing noise. Advanced timing gives crunchy noise under load. According to him, engine runs fine and noise only comes at 3 000 RPM and up, which means - load.
I found that CVTC on Nissans actually controls camshaft timing. If CVTC is failing, that may explain "timing" type noise. I am assuming, valve train has tappets instead of oil lifters and rockers are not adjustable?

[RED_DET]

Yes 3k miles and 3qts is outrageous, a 1/2 qt at 1k is still too much in my book. Rockers are not adjustable. Other issues you have to look at are timing chain and tensioner....It is hard to diagnose noises over the internet because crunch may mean something completely different than what it is.

[ukrkoz]

He just left. He called me at around noon on this. I told him to pour can of Seafoam inside and drive on it for a bit. Engine runs like a Swiss watch now. I had her up to 4 000 RPM without a slightest noise.
He will be checking on oil every 2 weeks from now on, and we'll switch her to 10WW30 instead of 5W30 synthetic. Will also add about half can Lucas to oil. I'll let him drive on Seafoam for about a month (She drives very little, will be only 500-700 mile) and we'll do oil change.
Thank you for friendly help. Much appreciated.

[ukrkoz]

Btw, does it have tappets or hydraulic lifters? I can not tell from picture in Haynes. Haynes calls them lifters. If it's hydraulic lifters, then lifters are going sticky. He'll need to Seafoam that engine twice a year. Not worth tearing it apart and replacing all that.

[audtatious]

Haynes sux...use the Infiniti FSM: http://www.nicoclub.com/FSM/G35/

[ukrkoz]

Thanks. Forwarding on to the rightful owners.